How The Universe Works Part 3: Alien Galaxies

Galaxies, home to stars, planets and us, come in all shapes and sizes. From majestic spirals to giant balls of stars and gas, these immense cities of stars are the building blocks of the Universe itself. How the Universe Works witnesses the evolution of galaxies; from clouds of cold gas 13 billion years ago, to the magnificent spirals that fill our night sky. Super-massive black holes, dark, giant monsters lurking in the heart of galaxies, and mysterious dark matter, the glue that holds galaxies together. Filaments of gas, link galaxies up in a colossal cosmic web to form the largest structure in the Universe and protects them from an even more enigmatic force”¦dark energy, that threatens to rip the universe apart.